The goal of the proposed study is to determine the molecular mechanism involved in germinal vesicle breakdown (GVBD) of Xenopus oocyte, induced by progesterone. During the induction period prior to GVDB, post-translation modifications of proteins occur. One of these modifying reactions is adenosine diphosphate (ADP) ribosylation, demonstrated by a rise in the activity of poly(ADP-ribosyl) synthetase in the germinal vesicle. Moreover, the cytosol and mitochondria fractions contain ADP-ribosyl transferase activity. The cytosolic enzyme was partially purified by chromatography on phenyl Sepharose, DEAE-Sephadex, NAD-agarose and ConA Sepharose. Approximately 7000 fold purification was achieved. In contrast to poly(ADP-ribosyl) synthetase, the transferase mediated mono-ADP-ribosylation and does not require DNA for activation. The enzymatic activity was also located in the intramembrane fraction of the mitochondria. The present aims are to purify and characterize the cytosolic and/or mitochondrial transferase system and to determine the acceptor molecules. This avenue of investigation will clarify the function of this post-translation modifying reaction. The bee venom, mellitin, is a cationic amphiphilic peptide and induced GVBD, simulating progesterone action. The venom works rapidly (2 to 4 hr), is effective at a concentration of 0.03 nM in vitro, and acts on the plasma membrane. However, this peptide causes mottling of the animal role resembling pseudomaturation. Our plan is to compare the molecular action of progesterone and mellitin on plasma membrane cyclase system and on pyruvate dehydrogenase of mitochondria. The results will contribute information on the molecular events involved in the induction of GVBD.